Andeson, 27, comes in on the back of a top domestic season for Canterbury, in which she topped the T20 batting charts with 536 runs at 59. She was subsequently in line for a call-up for the tour of Sri Lanka in July, but had to pull out due to a finger injury.
Auckland’s Armstrong, 23, will only play the T20Is in South Africa, replacing Izzy Gaze who is in South Africa for the ODI leg of the tour.
Coach Ben Sawyer was all praise for the duo. “Kate had an outstanding domestic season last year and was unfortunate to miss the Sri Lanka tour through injury,” he said. “We like her power and skills with the bat and we’re looking forward to giving her an opportunity on the international stage.
“Bella’s an exciting young prospect who hits the ball hard and is an outstanding fielder, so she’s got all the attributes that we want from a White Fern.”
New Zealand kick off the tour of South Africa with a warm-up one-dayer on September 21, followed by three ODIs and five T20Is. The squad will undergo a training camp before leaving for South Africa, from September 10 to 14, in Tauranga.
Allrounder Hayley Jensen was not considered for selection for the tour as she is yet to fully recover from the knee surgery she underwent in May.
New Zealand squad for the tour of South Africa: Sophie Devine (capt), Kate Anderson, Bella Armstrong (T20Is only), Suzie Bates, Bernadine Bezuidenhout, Eden Carson, Izzy Gaze (ODIs only), Maddy Green, Brooke Halliday, Fran Jonas, Melie Kerr, Molly Penfold, Georgia Plimmer, Hannah Rowe, Lea Tahuhu